Pedicle Screw Fixation System and Method for Use of Same

ABSTRACT

A pedicle screw fixation system and method for use of the same are disclosed. In one embodiment, a tulip is provided for holding a head of a pedicle screw substantially along a longitudinal axis. The tulip includes opposing first and second U-shaped receiving slots aligned along a transverse axis. A rod is received by the opposing first and second U-shaped receiving slots. A coupling collar includes a plurality of resilient fingers circumferentially disposed therearound such that a snap fit engagement with the head of the pedicle screw formed. The coupling collar includes a first deformable face operable for contact with the rod. A set screw is for adapted for driving engagement through the tulip along the longitudinal axis such that a second deformable face is positioned for contact with the rod. The first and second deformable faces conform to the shape of the rod in response to forceful engagement therewith.

PRIORITY STATEMENT & CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from co-pending patent application Ser.No. 61/119,312 entitled “Pedicle Screw Fixation System and Method forUse of Same” and filed on Dec. 2, 2008 in the names of Steve Courtneyand David Freehill; which is hereby incorporated by reference for allpurposes.

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to connection of an orthopedic rodto an anchoring element and, in particular, to a pedicle screw fixationsystem and method for use of the same for surgical use on the spinalcolumn of a patient for stabilization thereof.

BACKGROUND OF THE INVENTION

A large number of pedicle screws for fixation of the spinal column arealready known. The disadvantages of these pedicle screws includes therelatively complicated locking mechanisms for securing the orthopedicrod into a receiving member or tulip. In many cases, the head of thepedicle screw can be aligned with the position of the orthopedic rodonly to a limited extent, necessitating complicated bending of thelongitudinal bar to correct the angle. Alternatively, the tulips arepivotly mounted to the head of the pedicle screw by way of a universaljoint providing pivoting linkage therebetween. These pivoting linkages,while permitting the alignment of the orthopedic rod, have proventhemselves to lack the rigidity required during surgery to achieve andmaintain an accurate placement.

SUMMARY OF THE INVENTION

A pedicle screw fixation system and method for use of the same aredisclosed. In one embodiment, a tulip is provided for holding a head ofa pedicle screw substantially along a longitudinal axis in a pivotinglinkage providing polyaxial placement. The tulip includes opposing firstand second U-shaped receiving slots aligned along a transverse axis. Arod is received by the opposing first and second U-shaped receivingslots. A coupling collar includes a plurality of resilient fingerscircumferentially disposed therearound such that a snap fit engagementwith the head of the pedicle screw formed therebetween. The couplingcollar includes a first deformable face operable for contact with therod. A set screw is adapted for driving engagement through the tulipalong the longitudinal axis such that a second deformable face ispositioned for contact with the rod. The respective first and seconddeformable faces conform to the shape of the rod in response to forcefulengagement therewith; thereby, increasing the surface area of contacttherebetween and locking the tulip in position relative to the pediclescrew.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures in which correspondingnumerals in the different figures refer to corresponding parts and inwhich:

FIG. 1 is an illustrated view of one embodiment of a set of pediclescrew fixations systems implanted into a human vertebral column;

FIG. 2 is a side view of the pedicle screw fixation system of FIG. 1implanted into the human vertebral column;

FIG. 3 is a side elevation view of the pedicle screw fixation systemdepicted in FIG. 2, wherein for purposes of illustration the pediclescrew fixation system is not shown implanted into a human vertebralcolumn;

FIG. 4 is a second side elevation view of the pedicle screw fixationsystem depicted in FIG. 2, the view of FIG. 3 being 90° displaced fromthe view of FIG. 3;

FIG. 5 is a perspective exploded view of the pedicle screw systemdepicted in FIG. 2;

FIG. 6 is a top perspective view of one embodiment of a component, acoupling collar, of the pedicle screw system depicted in FIG. 2;

FIG. 7 is a bottom perspective view of the component depicted in FIG. 6;

FIG. 8 is a top perspective view of one embodiment of a component, a setscrew, of the pedicle screw system depicted in FIG. 2;

FIG. 9 is a bottom perspective view of the component depicted in FIG. 8;

FIG. 10 is a side cross-sectional view of the pedicle screw systemdepicted in FIG. 2 prior to application of force; and

FIG. 11 is a side cross-sectional view of the pedicle screw systemdepicted in FIG. 2 following the application of force.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts whichcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention, and do not delimit the scope of the presentinvention.

Referring initially to FIGS. 1 and 2, therein is depicted one embodimentof a set of pedicle screw fixation systems, individually andcollectively numbered 10, implanted into a humane vertebral column. Avertebral pedicle is a dense stem-like structure that projects from theposterior of a vertebra. There are two pedicles per vertebra thatconnect to other structures such as lamina and vertebral arches. By wayof example, the pedicle screw fixation system presented herein may beused to correct deformity, treat trauma, or a combination thereof.Additionally, such pedicle screw fixation systems may be used ininstrumentation processes to affix rods and plates to the spine or,alternatively, they may be used to immobilize part of the spine toassist fusion by holding bony structures together.

As shown in FIG. 1 and FIG. 2, the pedicle screw fixation systems 10 areplaced down the small bony tube created by the pedicle, which isrepresented by the letter P, on each side of the vertebra, between thenerve roots. This allows the pedicle screw fixation system 10 to grabinto the bone of the vertebral body, furnishing a solid hold in thevertebra. As illustrated, rods, such as orthopedic rod or rod R, connectthe pedicle screw fixation systems 10 together at two or moreconsecutive spine segments, such as lumbar segments 5 and 6.

Referring now to FIG. 3 through FIG. 5, therein is depicted oneembodiment of the pedicle screw fixation system 10 and rod R in furtherdetail. A pedicle screw 12 includes a threaded shaft 14 and aspherically-shaped head 16 integrally formed therewith at a shank 18. Inone implementation, a contact point 20 at the end of the threaded shaft14 includes an inclined plane. A socket 22 is located on the head of thepedicle screw.

A tulip 30 in the form of a receiving member includes a housing 32 forreceiving the pedicle screw 12 that is defined by a housing bore 34 onone end of a longitudinal axis L and an opening 36 on the other end ofthe longitudinal axis L. Two opposing U-shaped receiving slots 38, 40intersect the opening 36 and are aligned along a traverse axis T, whichis orthogonal to the longitudinal axis L. Internal threads 42 span theportion of the housing 32 between the receiving slots 38, 40. Thepedicle screw 12 is adapted to be inserted through the opening 36 andthe housing bore 34 along the longitudinal axis L of the tulip 30. Aspherical-shaped seat 50 is formed proximate to the housing bore 34 toaccept the head 16 of the pedicle screw 12 and provide a universal pointof contact 52 having a receiving space 54 (see FIGS. 10 and 11)thereabout to permit some angular displacement of the tulip 30 about thepedicle screw 12. In one embodiment, the universal point of contact 52provides a pivoting linkage for polyaxial placement of the pedicle screw12 relative to the tulip 30.

The head 16 of the pedicle screw 12 is located in contact with theinterior of the tulip 30 and, in one embodiment, the shape of the head16 conforms to the shape of the seat 50. The pivotal linkage formedbetween the head 16 and the housing 32 of the tulip 30 provides therigidity required during surgery to achieve and maintain an accurateplacement. This universal joint does not reposition with a minimum oraccidental amount of force, rather an intentional amount of force isrequired for positioning and repositioning. It should be appreciatedthat although the shape of the head and the shape of the seat 50 areillustrated as being complimentary spherical shapes, other shapes,including conical and pyramidal shapes, for example, are within theteachings presented herein.

FIG. 6 and FIG. 7 depict a coupling collar 60 that includes a pluralityof resilient fingers 62 circumferentially disposed about a body 63. Theresilient fingers 62 provide for a snap fit engagement with the head 16of the pedicle screw 12. A window 64 in the coupling collar extendstherethrough to furnish access to the socket 22. A deformable face 66 ispresented by the coupling collar 60 toward the opening 36. In oneembodiment, a pair of collapsible rings 68 create the deformable face66. The coupling collar 60 not only provides a surface of engagement aswill be discussed in further detail below, the coupling collar 60protects the head 16 and socket 22 from damaging torque and force duringinstallation of the pedicle screw fixation system 10.

FIG. 8 and FIG. 9 depict a driving member or in one specific embodiment,the set screw 70 that threadably engages the internal threads 42. Alower end of a body 71 of the set screw 70 presents a deformable face 72opposite to the deformable face 66 of the coupling collar 60. Threecollapsible 74 rings create this second deformable face 72. The upperend of the set screw 70 also includes a socket 78 for accepting theapplication of torque from a tool, such as an Allen wrench.Additionally, the sides of the set screw include threads 76 that areadapted to mate with the internal threads 42 of the tulip 30.

Although a set screw is depicted, it should be appreciated that thedriving member may be any mechanical device that engagingly travelsalong the longitudinal axis L of the pedicle screw fixation system 10 toapply force or torque to secure or lock the rod. With respect to thecoupling collar 60 and the set screw 70, these components are configuredto be positioned within the housing 32. Each of the coupling collar 60and the set screw 70 define respective contact surfaces that aredeformable in response to the application of torque and contact betweenthe respective contact surfaces and the rod R. Such application of forceincreases the surface area of the contact surfaces in contact with theouter surface of the rod R. In one embodiment, as shown, these contactsurfaces are smooth. It should be appreciated that these contactsurfaces may be roughed, serrated, ribbed, otherwise finished andprofiled to improve the engagement between the contact surfaces and therod R. Similarly, it should be understood that although a smooth rod isdepicted, the rod may be correspondingly roughed, serrated, ribbed orotherwise finished and profiled to further improve frictional engagementbetween the contacts surfaces of the coupling collar 60 and the setscrew 70 and the rod 70.

In one embodiment, the coupling collar 60 and the set screw 70 areconfigured to be positioned within the housing 32 such that the couplingcollar 60 is beneath rod receiving space 80 and the set screw is aboverod receiving space 80. The rod receiving space 80 also being formed bythe housing 32. In this embodiment, the rod receiving space 80 of thehousing 32 is interposed between the coupling collar 60 and the setscrew 70. In response to the application of force, the coupling collar60 and the set screw 70, or diving member, undergo a plastic deformationof metal and change form to more complement a contour of the outersurface of the rod R. In this manner, the coupling collar 60 and the setscrew 70 expand into the rod receiving space 80 not occupied by the rodR. More particularly, the coupling collar 60 and the set screw 70 mayexpand into the receiving space 54 and the receiving space 82.

Referring now to FIG. 10, in operation, the threaded portion of thepedicle screw 12 may be secured to a bone by first drilling a pilot holeinto the bone and then inserting the tip end or contact point 20 of thethreaded portion into the pilot hole. More particularly, the surgeon mayuse fluoroscopy, conventional x-ray, computer-assisted visualization oranother technique to determine the depth and angle for the screwplacement. A receiving channel is drilled and the screw is inserted. Asmentioned, the head 16 of the pedicle screw 12 is moveable, allowing itto swivel so as to defray vertebral stress.

The pedicle screw 12 provides a firm anchor points that can then beconnected to the rod R. A tool or driver, such as an Allen wrench, isthen inserted through the window 64 in the coupling collar 60 into thesocket 22 formed in the pedicle screw head. After the pedicle screw 12is torqued and securely anchored into the bone, the tulip 30 is free topivot and rotate relative to the pedicle screw 12 so that the orthopedicrod R may be positioned through the receiving slots 38, 40 and seatedtherein in contact with the coupling collar 60. The orthopedic rod R maybe tubular without any threads. After the orthopedic rod R ispositioned, the set screw 70 is threadably engaged with the internalthreads 42 of the tulip 30 and driven toward the orthopedic rod R untilthe lower end of the set screw 70 engages the orthopedic rod R. Asshown, the coupling collar 60 is positioned in a conformed fit 84 withthe seat 50 of the tulip 30.

With reference to FIG. 11, the set screw 70 continues to be driventhrough the internal threads 42 for applying a downward force on theorthopedic rod R, which, in turn, provides a downward force on the faceof the coupling collar 60. As the set screw 70 continues to advance,substantially simultaneously the collapsible rings 74 of at lower end ofthe set screw 70 and the collapsible rings 68 near the face of thecoupling collar 60 deform and expand to conform to the shape of theorthopedic rod R.

As a result, the deformed surface of the coupling collar 60 expands tofill the receiving space 54, thereby engaging the spherical head 16 ofthe pedicle screw 12, the interior housing 32 of the tulip 30, and theorthopedic rod R in order to lock the tulip 30 in place relative to thepedicle screw 12 and preventing further pivotal movement of the tulip 30relative to the pedicle screw 12. The force provided by the set screw 70does not cause the head 16 of the pedicle screw 12 to be pressed againstthe interior housing 32 of the tulip 30. Rather, the force provided bythe set screw 70 through the orthopedic rod R causes the deformation ofthe coupling collar 60 and pressing of the coupling collar 60 againstthe interior housing 32 of the tulip 30 and the pedicle screw 12 withinthe space therebetween.

Similarly, the collapsible or deformable face 72 of the set screw 70conforms to the orthopedic rod R, thereby providing an engagementbetween the orthopedic rod R and the set screw 70. The deformed surfaceof the set screw 70 expands to fill receiving space 82, thereby creatingan engagement. Moreover, in one embodiment, in a similar manner, thecoupling collar 60 defines and expands to improve the conformed fit 84between the coupling collar 60 and the seat 50 of the tulip 30. In thisway, the orthopedic rod R, the tulip 30, and the pedicle screw 12 arefixed.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. A pedicle screw fixation system comprising: a receiving member havinga housing for receiving a pedicle screw, the housing including internalthreads therein, the housing including a housing bore at a first end ofa longitudinal axis and an opening at a second end of the longitudinalaxis; opposing first and second U-shaped receiving slots intersectingthe opening, the opposing first and second U-shaped receiving slotsoperable for receiving a rod; the pedicle screw having a threaded shaftand a spherically-shaped head formed therewith at a shank, the pediclescrew being adapted to be inserted through the opening and the housingbore along the longitudinal axis; a socket located in thespherically-shaped head of the pedicle screw; a spherically-shaped seatformed within the housing, the spherically-shaped seat adapted to acceptthe spherically-shaped head of the pedicle screw; a coupling collarincluding a plurality of resilient fingers circumferentially disposedtherearound, the coupling collar adapted for snap fit engagement withthe head of the pedicle screw, the coupling collar having a firstdeformable face opposite to the plurality of resilient fingers; a windowextending through the coupling collar, the window providing access tothe socket; and a set screw for threadably engaging the internalthreads, an upper end of the set screw including a socket and a lowerend of the set screw presenting a second deformable face.
 2. The pediclescrew fixation system as recited in claim 1, wherein the housing furthercomprises a spherical-shaped seat adapted to a conformed fit with thecoupling collar.
 3. The pedicle screw fixation system as recited inclaim 1, wherein the rod further comprises an unthreaded tubular rod. 4.The pedicle screw fixation system as recited in claim 1, wherein thespherically-shaped seat provides a universal point of contact.
 5. Thepedicle screw fixation system as recited in claim 1, wherein thespherically-shaped seat further comprises a receiving space thereaboutto permit some angular displacement of the receiving member about thepedicle screw.
 6. The pedicle screw fixation system as recited in claim1, wherein the first deformable face of the coupling collar furthercomprises a pair of collapsible rings.
 7. The pedicle screw fixationsystem as recited in claim 1, wherein the second deformable face of theset screw further comprises three collapsible rings.
 8. The pediclescrew fixation system as recited in claim 1, wherein the window is sizedto accept a tool that engages the socket.
 9. A pedicle screw fixationsystem comprising: a tulip for holding a head of a pedicle screwsubstantially along a longitudinal axis, the tulip including opposingfirst and second U-shaped receiving slots aligned along a transverseaxis, the opposing first and second U-shaped receiving slots operablefor receiving a rod; a coupling collar including a plurality ofresilient fingers circumferentially disposed therearound, the couplingcollar adapted for snap fit engagement with the head of the pediclescrew, the coupling collar having a first deformable face operable forcontact with the rod; and a set screw adapted for driving engagementthrough the tulip along the longitudinal axis, a lower end of the setscrew presenting a second deformable face operable for contact with therod, wherein the first and second deformable faces conform to the shapeof the rod in response to forceful engagement therewith.
 10. The pediclescrew fixation system as recited in claim 9, wherein the tulip forholding the head further comprises a receiving space thereabout topermit some angular displacement of the tulip about the pedicle screw.11. The pedicle screw fixation system as recited in claim 9, wherein therod is operable to be set in contact with the coupling collar.
 12. Thepedicle screw fixation system as recited in claim 9, wherein the head islocated in isolated contact with respect to the rod.
 13. The pediclescrew fixation system as recited in claim 9, wherein the coupling collaris interposed between the rod and the head.
 14. The pedicle screwfixation system as recited in claim 9, wherein the coupling collarprotects the head from damaging torque and force during installation ofthe pedicle screw.
 15. The pedicle screw fixation system as recited inclaim 9, wherein the first deformable face of the coupling collarfurther comprises a pair of collapsible rings.
 16. The pedicle screwfixation system as recited in claim 9, wherein the second deformableface of the set screw further comprises three collapsible rings.
 17. Apedicle screw fixation system comprising: a tulip holding a head of apedicle screw substantially along a longitudinal axis of the tulip, thetulip including opposing first and second U-shaped receiving slotsaligned along a transverse axis for receiving a rod, the opposing firstand second U-shaped receiving slots operable for receiving a rod; acoupling collar having resilient fingers circumferentially disposedtherearound in snap fit engagement with the head of the pedicle screw,the coupling collar having a first deformable means for contacting witha rod; and means for advancing a set screw through the tulip along thelongitudinal axis, a lower end of the set screw presenting a firstdeformable means for contacting the rod, wherein the first and seconddeformable means for contacting shape to the rod in response to forcefulengagement therewith, thereby locking the tulip in position relative tothe pedicle screw.
 18. The pedicle screw fixation system as recited inclaim 17, further comprising a driving means for applying torque tosecure the pedicle screw to the bone, the driving means for applyingtorque for insertion into a socket formed in the head of the pediclescrew, the driving means for applying torque being inserted through awindow extending through the coupling collar.
 19. The pedicle screwfixation system as recited in claim 17, wherein the rod is seated incontact with the coupling collar.
 20. The pedicle screw fixation systemas recited in claim 17, wherein the set screw, during advancement alongthe longitudinal axis, threadably engages internal threads of the tulip.21. A method for using a pedicle screw fixation system with a bone, themethod comprising: providing a tulip holding a head of a pedicle screwsubstantially along a longitudinal axis of the tulip, the tulipincluding opposing first and second U-shaped receiving slots alignedalong a transverse axis, the opposing first and second U-shapedreceiving slots operable for receiving a rod; providing a couplingcollar having resilient fingers circumferentially disposed therearoundin snap fit engagement with the head of the pedicle screw, the couplingcollar having a first deformable face operable for contact with a rod;securing the pedicle screw to the bone; receiving the rod through thefirst and second U-shaped receiving slots; advancing a set screw throughthe tulip along the longitudinal axis, a lower end of the set screwpresenting a second deformable face operable for contact with the rod;and conforming the first and second deformable faces to the shape of therod in response to forceful engagement therewith, thereby locking thetulip in position relative to the pedicle screw.
 22. The method asrecited in claim 21, wherein securing the pedicle screw to the bonefurther comprises: inserting a tool into a socket formed in the head ofthe pedicle screw, the tool being inserted through a window extendingthrough the coupling collar; and applying torque to secure the pediclescrew to the bone.
 23. The method as recited in claim 21, whereinreceiving the rod through the first and second U-shaped receiving slotsfurther comprises seating the rod in contact with the coupling collar.24. The method as recited in claim 21, wherein advancing a set screwthrough the tulip along the longitudinal axis further comprisesthreadably engaging internal threads of the tulip with the set screw.